Homestuck is a online webcomic created by Andrew Hussie, and part of the MS Paint Adventures series. Started on April 13, 2009, the comic has reached over 4000 pages and continues to grow at an astounding rate.
Described by the author as 'a tale about a boy and his friends and a game they play together', Homestuck follows four children through seven acts (five of which have been completed so far, as well as two intermissions) as they test a game called Sburb which can manipulate the environment of the real world, ala The Sims or Spore. Although the comic starts out rather simple and lighthearted, it quickly becomes complex as alternate universes, time travel and interweaving story lines come into play. Along with the four 'main' children, the comic follows twelve Trolls who play a very similar game, only with much more dire consequences. As of the sixth act, four more new children have been introduced, as well as one more potential new Troll.
The comic contains many recurring elements which it is known for,
including chess, amphibians, meteors, the number 413, the
stuffed rabbit from the movie Con Air, and various other ridiculous nonsense.
These gags have become rather well known outside of the community, and
some have even mutated into memes of their own right. Homestuck is also known for the way it presents itself: not as a typical comic, but more along the lines of an interactive game, where the link to reach the next page is often a command to the character, even during the long narrative sections. Also, rather then having actual speech, most of the game's dialogue is conveyed through chat logs, complete with horrible 'typing quirks'. Although many of the 'typing quirks' are nigh unreadable, it's often recommended to read the logs anyways, as many of them contain valuable information relevant to the plot (and understanding Homestuck in general).
Due to the sheer dedication required to make one's way through all 4000+ pages, Homestuck has acquired a dedicated fan base which often provides fan art, remixed music and even suggestions for the comic itself, even though Hussie announced at the beginning of the comic that he would not take suggestions. Many characters who were originally planned to have lesser roles have been given more important parts due to reader popularity, such as Gamzee Makara, one of the Trolls. The fan base is also known for being incredibly dedicated to their ships, more so then most communities (probably due to the fact that it is canon for characters to get into four different types of relationships), and it is often ill-advised to bring up 'controversial' pairings when talking to Homestuck fans (such as JohnxKarkat, GamzeexTavros, or FeferixAnybody, amongst others). Another common feature of the fan base is the sheer number of fan characters that it has produced, many of them of negligible quality. The sheer amount of these characters is so prevalent that it has become a common joke for veterans to say 'show me yours and I'll show you mine' to newcomers, under the assumption that everybody will have at least one 'bad Homestuck OC'. This fire has also been fueled by a recent statement from Hussie on his Tumblr declaring that all fan Trolls were now canon... even the shitty ones.
Homestuck is often described as a webcomic for the criminally insane, socially uneducated, and 'those who enjoy feeling like they've just blown their brains out onto a concrete wall'. While all three of these descriptors are often true when it comes to the Homestuck fandom, the comic itself provides a exquisite, if not incredibly challenging read, and often the payoff when one finally reaches the end of an act or can finally make a conclusion about a character or event can be compared to a brain orgasm. It is often considered a must read for webcomic enthusiasts.
The first page of Homestuck can be found here.